Technical Field
The present disclosure relates to an exhaust gas purification apparatus of an internal combustion engine provided with a NOx absorption/discharge device which can absorb nitrogen oxide (NOx) included in an exhaust gas and discharge the absorbed nitrogen oxide.
Description of the Related Art
An exhaust gas purification apparatus for purifying nitrogen oxide discharged from an internal combustion engine is described in JP 2009-112967 A. This exhaust gas purification apparatus (hereinafter, will be referred to as “the conventional device”) comprises adsorption means and purification means provided in an exhaust passage. The adsorption means adsorbs the nitrogen oxide thereon and the purification means reduces the nitrogen oxide to purify the nitrogen oxide.
The adsorption means is provided in the exhaust passage upstream of the purification means. The purification means can purify the nitrogen oxide when a temperature of the purification means is relatively high. The nitrogen oxide adsorbs on the adsorption means when a temperature of the adsorption means is relatively low. In particular, the nitrogen oxide adsorbs on the adsorption means when the temperature of the adsorption means is a temperature which corresponds to the temperature of the purification means when the purification means cannot purify the nitrogen oxide. On the other hand, the nitrogen oxide adsorbing on the adsorption means desorbs from the adsorption means when the temperature of the adsorption means becomes high. In particular, the nitrogen oxide adsorbing on the adsorption means desorbs from the adsorption means when the temperature of the adsorption means becomes a temperature which corresponds to the temperature of the purification means when the purification means can purify the nitrogen oxide.
According to the conventional device, when the temperature of the purification means is relatively low, in particular, when the temperature of the purification means is a temperature, at which the purification means cannot purify the nitrogen oxide, the nitrogen oxide included in the exhaust gas adsorbs on the adsorption means.
When the temperature of the purification means becomes high, in particular, when the temperature of the purification means becomes a temperature, at which the purification means can purify the nitrogen oxide, the nitrogen oxide adsorbing on the adsorption means desorbs from the adsorption means and then, flows into the purification means. Thereby, the nitrogen oxide is purified by the purification means.